Double-chain stitch zigzag sewing machine



K. NICOLAY DOUBLE-CHAIN STITCH ZIGZAG SEWING MACHINE Filed Nov. 26, 1965 April 9, 1968 3 Sheets-Sheet 2 April 9, 1968 K. NICOLAY DOUBLE-CHAIN STITCH ZIGZAG SEWING MACHINE Filed Nov. 26, 1965 Fig.5

5 Sheets-Sheet 5 Karl Nicolag INVENTOR.

' Attorney United States Patent O 3,376,837 DOUBLE-CHAIN STITCH ZIGZAG SEWING MACHINE Karl Nicolay, Bielefeld, Germany, assignor to Durkoppwerhe G.m.b.H., a corporation of Germany Filed Nov. 26, 1965, Ser. No. 509,724 Claims priority, application Germany, Nov. 26, 1964, D 45,919 9 Claims. (Cl. 112-158) ABSTRACT OF THE DISCLOSURE A double-chain stitch zigzag sewing machine in which the needle and a gripper beneath the sewing table are displaced synchronously so that the gripper describes a generally orbital path, a finger fixedly positioned with respect to this path having a projection extending into a groove along the side of the gripper blade for controlling the formation and release of the thread loop below the table. The gripper has a protuberance along whose flanks the stretches of the loop are guided.

In the specification My present invention relates to a doublechain stitch zigzag sewing machine wherein the sewing needle is oscillated transversely to the direction of stitch formation and engages the fabric on opposite sides of a median plane extending transversely to the fabric in the direction of advance thereof in alternate penetrations of the fabric and the stitching needle co-operates with an orbital gripper below the fabric for producing the chain stitch.

It is common practice in the sewing of chain stitches on zigzag sewing machines to provide an auxiliary gripper designed to form a loop below the fabric in the upper thread in co-operation with the needle upon an initial penetration of the fabric and to hold this loop until the needle passes through, in a successive penetration, the so-called thread triangle formed between the upper-thread loop and an underthread and maintained by the main gripper below the fabric. Such arrangements require special control and drive elements for the auxiliary gripper and are, therefore, relatively complex and costly. Furthermore, they are disadvantageous from a point of view of efficiency of the machine because the normal machine drive is frequently overloaded even from the point of view of ordinary zigzag stitching.

It has also been proposed to provide elastic retaining bodies which co-operate with and are mounted upon the main gripper whereby overstitch widths of up to 2 mm. can be obtained. Such devices, generally arranged on the underside of a gripper plate lying in a horizontal plane and notched to accommodate the needle-thread loop, are designed to hinder or brake the withdrawal of the loop from the gripper plate. These devices are not, however, successful for the production of chain stitches with zigzag sewing machines wherein overstitch widths from 2 mm. to about 4.5 mm. are required. For the latter purpose, two elastic retaining bodies are provided, of which one cooperates with the upper edge of the gripper plate for engagement with the stretch of the needle-thread loop which passes over the forward side of the gripper plate upon entry of the needle into the thread triangle for retaining this stretch. The second retaining body cooperates with the lower edge of the gripper plate for retaining the thread triangle also during the passage of the needle through the latter.

Since such elastic retaining bodies are mounted upon the gripper or the gripper holder and are movable with the gripper, they add substantially to the mass which the gripper drive is required to displace and thus disadvan- 3,375,837 Patented Apr. 9, 1968 tageously influence this drive although they are somewhat less expensive and less complicated than auxiliary grippers. An even more significant disadvantage is the fact that these resilient retaining bodies each act upon threads of different thickness and texture in different ways so that the retaining force differs from thread to thread. F urthermore, the grippers must be adjusted for each thread thickness and/ or texture employed, thereby increasing the care which must be practiced, the labor cost and the possibility of problems resulting from overlooking the need for resetting the device for the particular thread.

It is the principal object of the present invention, therefore, to provide an improved mechanism in a doublechain stitch zigzag sewing machine which permits the formation of the thread triangle between the gripper or underthread and the needle or upper-thread loop for a wide range of overstitch widths whereby adjustment of the mechanism for each particular thread characteristic is not required and the drive of the sewing machine can be efiYected with greater assurance and without overloading.

A more specific object of this invention is to provide a mechanism, in a sewing machine of the character described, which will be capable of providing relatively large overstitch widths without the need for auxiliary devices mounted upon the gripper or mechanisms for displacing such auxiliary devices.

Still another object of this invention is to provide means, in an apparatus of the aforedescribed type, wherein a clamping of the needle or upper thread to the gripper plate is obviated and the release of the needle-thread loop can be effected in a precisely determined location without the need for special care to ensure that the device is adjusted for the particular thread characteristic and without a reduction in the efficiency of the sewing machine.

These objects and others which will become apparent hereinafter, are attained in accordance with the present invention, through the provision, in a zigzag sewing machine having a vertically reciprocable needle swingable from side to side transversely to the direction of fabric feed, of an orbital gripper means having a gripper blade engageable with an overthread loop formed beneath the fabric upon an initial insertion of the needle into and its withdrawal from the fabric, this gripper blade being movable in a generally elliptical path with its major axis substantially parallel to the line of swinging movement of the needle and thus transverse to the direction of fabric displacement.

The gripper blade, according to the present invention, engages this overthread loop below the fabric and is provided at a rearward portion with a retaining edge while its forward end engages an underthread so as to form between the overthread loop and the underthread the so-called thread triangle into which the needle passes during its subsequent insertion into the fabric, the gripper blade co-operating with a fixedly positioned finger adjacent its generally elliptical path and having a head or projectinon received in a groove in the gripper blade extending on opposite sides of the retaining edge for holding the overthread during movement of the gripper along its rearward stroke and thereby controlling the casting-off or shedding of the overthread. Thus, the overthread loop which would normally be cast otf freely from the gripper during its rearward stroke after the needle has passed through th fabric in its second pass of each threadforming cycle, is restrained by the braking action of the finger and the gripper blade which clamps the overthread between the fixedly positioned finger and the blade as it passes therealong. According to a particularly advantageous feature of this invention, the forwardly facing flank of the gripper is provided with a protuberance defining with a recess in the gripper blade the aforementioned retaining edge, this protuberance having a relatively shallow flank remote from the retaining edge for guiding the overthrcad loop onto the gripper without difficulty. The flank of the protuberance proximal to the retaining edge is, however, relatively steep so as to restrict withdrawal of the thread loop until the gripper has co-operated with the finger, as will become apparent hereinafter. The finger can be provided with a projection or head extending into the longitudinal groove of the gripper blade during the rearward movement of the gripper which, in the course of its elliptical path, moves toward the finger concurrently with the commencement of the rearward movement.

The head or projection of the finger is provided with a thread-lifting or thread-shedding edge which extends toward the gripper blade beyond the retaining edge so as to lift th thread from the retaining edge and over the protuberance during this rearward movement of the gripper. Furthermore, part of the finger, namely, the projection, is provided with a braking edge which clamps the overthread against a wall of the groove to restrain the thread upon its withdrawal from the gripper.

Thus, the thread-liftin. edge of the finger can engage the stretch of the overthread or needle-thread loop disposed at the retaining edge to co-operate with the gripper during its rearward movement and carry it over the protuberance of the gripper and onto the thread-braking edge whereby the shedding of the loop is hindered. Under these circumstances, the thread triangle is maintained during the subsequent penetration of the needle without disadvantageously influencing the stitchorming operation. The thread-lifting edge and the thread-brake edge form, according to this invention, a notch which extends in the direction of the protuberance therebeyond so that the thread can be retained in the notch for a period at least sufficient to permit it to clear the protuberance during retraction of the gripper. The projection edge confronting the gripper is inclined away therefrom in the direction of the rearward movement of the gripper to ensure a positive thread-braking action.

According to still another feature of this invention, means is provided for controlling the height of the finger with respect to the orbital path of the gripper and for adjusting the distance of the head of the finger from this path. Such adjusting means can include a pair of positioning screws and can serve as part of the mounting means which connect the finger to the housing of the gripper-displacement mechanism. The latter is, of course, coupled with the needle drive so that the needle and the gripper blade operate synchronously.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing, in which:

FIG. 1 is a side-elevational view of a double-chain stitch zigzag sewing machine according to this invention with the improved mechanism shown in partial crosssection;

FIG. 2 is a perspective view of the gripper plate, according to this invention, in its thread-triangle forming position wherein the needle-thread loop is passed beneath the gripper plate during its forward movement;

FIG. 3 is a similar perspective view showing the cooperating elements of the gripper assembly in their position in which the needle enters the thread triangle upon retraction of the gripper plate;

FIG. 4 is an enlarged detail view in cross-section along the line IV-IV of FIG. 3;

FIG. 5 is a perspective view of the assembly in the course of release of the thread triangle; and

FIG. 6 is a perspective view of a portion of the assembly, partly exploded, showing the finger co-operating with the gripper and the means for presetting same.

In FIG. 1, I show a double-chain stitch zigzag sewing machine with parts broken away to reveal the mechanisms essential for the operation of the present invention; basically, the sewing machine comprises a machine bed 1 forming a table for the fabric and overhung by an arm 2 containing, in its head, the usual needle-rod drive. The needle 4, which is provided with an eye 4 for receiving the overthread from a spool or bobbin (not shown), is removably received in the needle rod 3 which, as can be seen from FIG. 1, is vertically shiftable within a swinging frame 5. The rod 3 can be provided with an actuating mechanism generally designated 2" in the head 2 for its vertical movement within the frame 5 and for the swinging movement of the frame in a plane transverse to the direction of fabric feed (arrow 2a). The zigzag drive 2" is conventional and need not be described in detail herein.

During vertical displacement of the needle 4, it co operates with an orbital gripper 6 which, also in a conventional manner, is coupled by a suitable actuating mechanism 6' for synchronous operation with the needledrive mechanism 2". The gripper-displacement mechanism can include a cam and/ or crank arrangement for the nutational displacement of the gripper via an output shaft 9 protruding from the mechanism housing 8 and provided with a support arm 10. The mechanism can include a shaft 6a coupled by a positive-entrainment belt 6b with the driving member 2b of the ncedle-aetuating mechanism 2". The shaft 6a extends at 60 via oilpermeatcd packings 603' into the closed housing 8 which is sealed against escape of oil and can have oil supplied to it via the usual oil ducts and wicks 6e in the table 1. The nutational mechanism 8 thus cause a generally elliptical movement of the gripper 6, which is adjustably mounted in the arm 10 by a screw 10' with the major axis of the orbital path of the gripper blade 6 extending transverse to the direction of feed of the fabric (arrow 21: in FIG. 5).

As can be seen from FIGS. 2-5, the formation of the thread-triangle 12 below the fabric F is effected by the needle-thread or overthread thread loop 13 and the gripper thread or underthread 14 with the aid of the gripper 6 whose blade 6 is provided at a forward end with a pas' sage 6a" through which the gripper thread 14 passes from a spool or bobbin, not shown. The gripper 6 is provided along the forward flank of its gripper blade 6 with a retaining protuberance 15. The flank of protuberance 15 rises gradually from the tip 6" of the gripper blade 6' but falls off sharply approximately at the center of the gripper blade 6' at a recess 15" to form a retaining edge 15 in which the overthread 13 can be seated. Thus, during the forward movement of the gripper blade 6' (arrow in FIG. 2) the tip of the blade passes through the overthread loop 13 so that the overthread pass 13" along the forward flank of the gripper blade 6' (FIG. 4) leads up along the protuberance 15 until it drops into the retaining edge 15' (FIG. 2). The steep flank of the protuberance 15 and this retaining edge 15 draw the loop 13 rearwardly during the rearward movement of the gripper blade 6' along its orbital path (FIG. 3).

To control the movement of the overthread loop 13 during the subsequent penetration of the needle 4 into the thread triangle 12 (FIG. 2) the forward flank is provided with a groove 16 above the thread channel 6b (FIG. 4). A projection 17 of the upright finger 17 extends into the groove 16, which lies on opposite side of the protuberance 15, during the rearward movement of the gripper 6. The tip or projection 17' of finger 17 is provided with a thread-rising edge 18 which extends intothe groove 16 below the retaining edge 15', and a threadbrake edge 19 as well as a guide edge 20 at a notch 21 which has a depth somewhat greater than the length of the protuberance 15 beyond the tip 18' of the threadlifting edge (FIG. 4). Thus, the perpendicular depth of the notch 21 from the forward edge of tip 17' is greater than the height of the protuberance 15 from the base of the groove 16. The thread-lifting edge 18 is inclined away from the forward end of tip 17' in the direction of the rearward movement of the gripper 6. The extremity of the thread-lifting edge 18 merges into the guide edge 20 and the thread-brake edge 19 so that the latter, as can be seen especially from FIG. 5, has a rising cross-section somewhat parallel to the juxtaposed edge of the wall of channel 16. Thus, a clamping of the loop 13 is effected between the thread-brake edge and this wall.

In order to provide the aforedescribed adjustability of the finger 17, and thus the location of the projection 17, the thread-lifting edge 18, and the thread-brake edge 19 with respect to the gripper blade 6' and its groove 16 or its elliptical transport path, the finger 17 (FIG. 6) is adjustably mounted on the cover plate 7 of the gripperdrive housing 8. The adjusting means can include a pair of adjusting screws for respective positioning of the finger 17 with regard to the height of the transport path and with regard to its lateral location relative thereto. For this purpose, the finger is formed as a rod of band-like metal and is attached by screws 22 passing through slots 23 in the finger 17 to the cover plate 7. The cover plate is provided with a vertical channel 30 accommodating the finger 17. For the precise positioning of the tip 17' with respect to the width of the channel 16, the adjusting mechanism 27 is provided. This mechanism can include a screw 24 threadedly received in an inwardly bent flange 17" of the finger 17 remote from the tip 17 and underlying the cover plate 7. The screw 24 bears against the underside of the cover plate 7 and is provided with a counter nut 25 to lock the adjustment at the desired height. After positioning of the finger, the screws 23 can be tightened to prevent any further vertical displacement.

An adjusting mechanism is similarly provided for varying the depth to which the projection 17' extends into the groove 16. This mechanism includes a screw 26 threaded into the finger 17 and bearing upon the front face of the plate 7 in the channel 30, the screw 26 being similarly provided with a locking nut 26. As the screw 26 is threaded into the finger 17, the latter is biased outwardly against its inherent resilient force for small movement relative to the gripper path. Furthermore, the finger is thus spring-loaded and forms a leaf spring requiring only minute displacement during operation of the device so that the spring characteristics are again substantially constant during operation.

For further adjustment of the finger 17 parallel to the major axis of the gripper path, the cover 7 is mounted upon the housing 8 by screws 29 which pass through arcuate slots 28 so that the cover can be limitedly displaced, upon loosening of the screws 29, angularly about the axis of shaft 9. It is thus possible to position the threadlifting edge 18 so that it sooner or later lifts the needlethread loop over the protuberance 15 during the rearward movement of the gripper.

Operation When the needle 4 moves upwardly from its lower position after an initial penetration of the fabric for a particular zigzag stitch, it produces the overthread loop 13 which is engaged by the gripper blade 6 at the beginning of its forward stroke along the elliptical path, this forward pass lying some distance beyond the finger 17. The gripper 6 takes up the loop 13 with its point 6" and the loop is thus carried onto a rearward portion of the gripper blade 6 beyond the protuberance 15. At the end of this upward movement of the needle 4, the thread 13 is held by the retaining edge 15' (FIG. 2).

As the gripper 6 commences its rearward stroke and passes proximally to the finger 17, the needle 4 again begins a penetration stroke. The tip 17 of the finger 17 enters the groove 16 and picks up the loop 13 from the gripper which is withdrawn along the finger while the needle enters the thread triangle 12. This thread triangle is of a size sufiicient to permit the swingable needle 4 to enter it as the needle alternately passes on the loop-forming side and the triangle side of the gripper. The stretch of the loop is held back by the tip 17' until its lifting edge 18 passes the region of the retaining edge 15' (FIG. 3) and engages the loop during the withdrawal stroke (FIG. 4). During further movement of the gripper in its rearward pass, the thread-lifting edge 18 picks up the loop 13 and lifts it over the protuberance 15 whereby the loop is freed. The loop then passes along the guide edge 20 to the thread-brake edge 19. As can be seen in FIG. 5, the loop stripped from the gripper blade 6 is clamped frictionally so that the thread triangle is retained during the movement of the needle on its descent without endangering the stitch formation.

The invention described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the appended claims.

I claim:

1. In a double-chain stitch zigzag sewing machine having a fabric table, an arm overhanging said table, and an overthread-entraining zigzag stitching needle vertically reciprocable on said arm for engagement with a fabric moved past a stitching location on said table on successively opposite sides of a median line extending generally in the direction of fabric feed, the combination therewith of gripper means in said table below said fabric having a gripper blade engageable upon a forward movement thereof with an overthread loop formed upon insertion of said needle through and withdrawal from said fabric during a first stitch for producing between said overthread loop and an underthread engageable by said gripper means a thread triangle adapted to receive said needle upon a successive insertion thereof through said fabric to form a double-chain stitch; means for displacing said gripper blade synchronously with said needle in a generally orbital path at said stitching location with a major axis of said path transverse to the direction of fabric feed, said gripper blade having a retaining edge for entrainment of said overthread loop upon a rearward movement of said gripper blade; and a finger fixedly positioned on said table with respect to said location and disposed adjacent said path for engagement with said overthread loop during rearward movement of said gripper blade for controlling the casting-off of said overthread loop by said gripper blade, said gripper blade being provided wit-h a protuberance extending generally in the direction of fabric feed and with a recess adjacent said protuberance, said retaining edge being formed by a flank of said protuberance and a wall of the recess, said protuberance tapering in the direction of said forward movement, said gripper blade being further provided with a longitudinally extending groove generally in the direction of the major axis of said path and extending on opposite sides of said edge, said groove opening in the direction of said finger and said finger having a projection extending into said groove during said rearward movement of said blade.

2. The combination defined in claim 1 wherein said projection is formed with a notch engageable with said overthread upon displacement of said gripper blade during said rearward movement, said notch being open in the direction of said blade and having a depth greater than the height of said protuberance whereby a thread received in said notch can clear said protuberance upon said displacement of said blade past said finger.

3. The combination defined in claim 2 wherein said projection has a thread-braking edge adjacent said notch for frictional clamping engagement of the overthread between a wall of said groove and said thread-braking edge during said rearward movement of said blade.

4. The combination defined in claim 3 wherein said notch is defined in part by a thread-lifting edge remote from said thread-braking edge, said thread-lifting edge extending toward said gripper blade past said retaining edge for removing the overthread therefrom upon relative movement of said gripper blade and said finger to bring the thread resting on said retaining edge into engagement with said thread-lifting edge.

5. The combination defined in claim 2, further comprising means for adjusting the location of said finger with respect to said path.

6. The combination defined in claim 5 wherein said gripper means includes a housing, mechanism in said housing for imparting orbital movement to said gripper blade, and adjusting means for selectively positioning said gripper blade relatively to said mechanism, said finger being mounted on said housing and provided with a first positioning screw for selectively varying the location of said finger with respect to said path in a horizontal direction, and a second positioning screw for selectively varying the height of said finger.

7. The combination defined in claim 6 wherein said gripper blade is supported at a rearward extremity and has a free forward end provided with an aperture adapted to receive said underthread.

8. The combination defined in claim 6 wherein said adjusting means for selectively positioning said gripper blade with respect to said mechanism includes a support shank forming part of said mechanism and having a socket, said gripper blade having at a rearward extremity a support member receivable in said socket and screw means for selectively locking said member in said socket.

9. The combination defined in claim 2 wherein said groove is provided with a wall extending in the direction of said finger beyond said retaining edge for ensuring a positive seating of the overthread in said notch.

References Cited UNITED STATES PATENTS RICHARD J. SCANLAN, JR., Primary Examiner. 

